Pelvic Inflammatory Disease (PID) is a common disease among young women that results in serious sequelae including infertility, recurrence, and chronic pelvic pain. Although Neisseria gonorrhoeae and/or Chlamydia trachomatis are recovered from approximately a third to a half of women with PID, in the other women the etiologic agent is often unidentified. Several studies have linked Mycoplasma genitalium with drug-resistant urethritis in men, but the role of M. genitalium in PID and its sequelae has been little studied. The great majority of American women with suspected PID are treated with antibiotic regimens directed toward gonorrhea and chlamydial PID. However, M. genitalium belongs to a class of bacteria called mycoplasmas, differentiated from other bacteria by lack of a cell wall. Therefore, it is likely resistant to cell wall inhibiting cephalosporins, including cefoxitin. Additionally, other mycoplasmas have demonstrated considerable resistance to tetracyclines. We propose that women with M. genitalium upper genital tract infection treated with current PID regimens may experience persistent infection and reproductive morbidity. We propose an M. genitalium polymerase chain reaction (PCR) study of 831 women in the ongoing PID Evaluation and Clinical Health Study. Using stored baseline and 30 day cervical and endometrial specimens, we propose to: 1) identify the risk factors for M. genitalium infection of the lower and upper genital tract; 2) determine the associations between M. genitalium, endometritis, and cervicitis; 3) describe the clinical features of women with upper and lower genital tract M. genitalium infection; 4) assess the treatment response of M. genitalium to cefoxitin and doxycycline; and 5) evaluate the impact of M. genitalium infection on reproductive morbidity. Exploring the role of M. genitalium in PID is imperative to optimize diagnosis and treatment and prevent reproductive morbidity among women with nongonococcal/nonchlamydial PID.